US2568539A - Film stabilizer for sound motionpicture projectors - Google Patents

Description

P 1951 J. BRISKIN ET AL 3 FILM STABILIZER FOR SOUND MOTION-PICTURE PROJECTORS Filed Nov. 20, 1947 2 Sheets-Sheet 1 {II I H m 'I W IIWHHM. HHIML @1 ill/[Ill]; N r .3

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FILM STABILIZER FOR SOUND MOTION-PICTURE PROJECTORS Filed Nov. 20, 1947 2 Sheets-Sheet 2 n Q i II N 0 I] l I N z NIQ h Q INVENTORS. fitkflga w 8 N Q m ud 350 Patented Sept. 18, 1951 FILM STABILIZER FOR SOUND'MOTION- PICTURE PROJECTORS,

Jack Briskin and Conrad Peto, Chicago, 111., as-

signors to Revere Camera Company,,0hicag o, 111., a corporation of Delaware Application November 20, 1947; Serial No. 787,188

4 Claims. 1

This invention relates to sound motion picture projectors, and more particularly to a stabilizer adapted to be used therewith for achieving constant velocity film travel at the point wherethe sound track of the film is scanned.

One object of the invention is to provide a stabilizer that cooperates with the film to oppose and moderate fluctuations occurring in the velocity of film travel. As is well known, mechanical film driving mechanisms are more or less incapable of uniform, unvarying operation. Velocity fluctuations are introduced through motor speed variations due to line and load variations. Also, the various. mechanical elements making up the power train such as bearings, shafts, gears and the film itself all are somewhat responsible for producing. fluctuations in the velocity of film travel. These fluctuations, if not substantially eliminated, introduce distortion in the sound pick-up system to thus substantially affect the sound reproduction characteristics of the projector. The present stabilizer concerns itself with means for eliminating these objectionable film velocity fiuctuationsj Another object is to provide a stabilizer that greatly simplifies the operation of properly threading the film through the projector. In prior projectors of this general character, it has been necessary to thread the film in such a manner as to eliminate all film slack between the various reels, driving sprockets, idling pulleys, etc. This makes the threading operation somewhat critical, and it introduces difiiculties for the amateur operators that ordinarily use this type of equipment. The invention eliminates the critical aspects of film threading by providing that more or less film slack may be present without interfering with the proper operation of the projector.

Still another object is to provide a film positioning device adapted to insure proper relationship between the film and the sound head upon which the sound track of the film is scanned.

Another object contemplates a stabilizer that is selectively movable to facilitate film threading through the stabilizer itself. Also, the stabilizer is self-adjusting so as to compensate for variations in film thickness that often are present.

Other objects and advantages of the invention will be apparent as the description proceeds, reference being had to the accompanying drawings wherein one form of the invention is shown. It is to be understood that the description and drawings are illustrative only, and are not to be taken as limiting the invention except insofar asit is limited bythe claims.

In. the drawings:

Fig. .1. is aside elevational, view ofjan-improved projectorv showing various, film guiding elements in simplifiedform;

Fig. 2. is a view on line 2 2.of Fig. 1, partly in section, showing the, stabilizer ofthe invention;

Fig. 3 isanend View, looking fromtheleft of Fig. 2, of a portion.of.tl'ie stabilizer;

Fig. 4 is aperspective view of a pivotal coupling that may be usedwith the invention;

Fig. 5 is a sectionalview on.5.5 of Fig. 2;

Fig. 6 is aview partly in section ofv our stabilizer;

Fig. '7 is afragmentaryplane view of the film used with the inventiomand Figs. 8. and.9 show. the..manner. in which the film. engages certain elements ofv the stabilizer.

Referring to. the. drawings, Fig. 1 shows in somewhat. simplified forma sound motion picture projector embodying the. present invention. The projector has an upper reel, I2 containing film l3 that threads. throughthe apparatus and is. wound. on lower, reel. I4 during projector operation. In the usualcase, lower reel [4 is motor driven while upper reel I2 is an idler.

Film [3 passes over idler pulley l5 and around drivesprocket IS, the film being held in engagement withsprocket vH'i'by means of retainer IT. The film, following a free loop 18', passes through the opticalv system ofv the projector, generally: indicated at 19, where the film is intermittently advancedin any well known manner.

After passing through optical system I9, the film may be freely looped as shown at 2!] after which it passes around the outside of sound head 2| where. the sound scanning takes place. The sound. head 2| may take the form of. a cylindrical member having asmall, light admitting aperture in the cylinder wall. A photoelectric cell (not shown) is mounted within the cylinder, the photosensitive electrode of the cell being in alignment with the aperture. A light source 22 and a lens system 23.are so alignedwiththe aperture and the. photosensitive electrode. that suitable illumination is provided for cooperation with the sound track of the film. The sound head 2| and its-associated instrumentalities are so disposed that'the soundtrack of the film passes over the light admitting aperture.

A structuregenerally shown at 25 bears against film I3' to hold' the film against sound head- 2| and, as will-be seen, to exert a stabilizing influence overthe velocity of film travel, thus insuring constant film velocity with respect to the sound-head. The structure25' also insures proper relationship between film l3 and sound head 2|.

Following sound head 2 I, film l3 passes around idler pulley 26, driving sprocket 21, idler pulley 28 and thence to lower reel I4. A retainer 29 insures proper film relationship with driving sprocket 21.

Certain dotted lines appearing in Fig. 1 show alternative positions that might be assumed by film l3 in the vicinity of sound head 2 I, thus demonstrating the non-critical aspect of the invention insofar as threading the film is concerned. It will be understood that the loops indicated will tend to vary in size upon starting and stopping of the projector as compared to their size during projector operation. The variations permitted in the size of these loops tend to insure trouble-free operation of the projector despite projector starting and stopping during the showing of a single reel of film.

Referring now to the other figures in the drawings, our improved stabilizer includes a rotatable drum 30 (at the right in Fig. 6) disposed in effective relationship with sound head 2|. The above mentioned, light admitting aperture in sound head 2| is shown at 3| in Fig. 6. The aperture desirably is sealed by glass so that the enclosed photoelectric cell is isolated from the sometimes dust laden atmosphere.

The rotatable drum 30 may form one end of a shaft 32 as illustrated. An inertia member such as flywheel 33 is carried at the other end of shaft 32. Drum 30, shaft 32 and flywheel 33 are substantially enclosed by a housing 34 that extends transversely of the projector through an opening 35 in the projector side 36.

Apair of vertically spaced brackets 38 and 39( Fig. 2) extend inwardly of the projector from side 36. The flywheel enclosing portion 40 of housing 34 is provided with top and bottom hollow lugs 42 and 43 (Figs. 2 and 3) that are in alignment respectively with the free ends of brackets 38 and 39. The hollow lugs 42 and 43 have countersunk portions that receive resilient members 44 and 45. These members may take the form of natural or synthetic rubber washers, and they engage the heads 46 and 41 of bolts that extend through openings in lugs 42 and 43 into threaded relation with the free ends of brackets 38 and 39.

The bracket engaging face 48 (Fig. of lug 42 tapers to a central ridge 49 that bears against bracket 38 as clearly shown in Fig. 5. The openings in lugs 42 and 43 are somewhat larger than the bolts passing therethrough, and therefore the coupling just described provides a pivotal relationship between the portion 48 of housin 34 and the brackets 38 and 39 associated with the projector side. The resilient members 44 and 45 in the lugs cooperate with the bolts, the enlarged lug openings and the ridge 49 to make possible this pivotal coupling.

Referring particularly to Fig. 6, the shaft 32 is mounted for free and easy rotation within housing 34. The left end of the portion 40 of housing 34 has a boss 52 that contains bearing elements for rotatably mounting reduced end 53 of shaft 32. These bearing elements include a dust shield 54, an inner race 55, ball bearings 56, an outer race 51, a bearing loading plunger 58, an oil washer 59 .and a loading spring 68. A plate 6| maintains the above mentioned hearing elements in proper position within boss 52.

The other end of shaft 32 has a reduced portion -63 that is rotatablymounted in bearing elements that are substantially similar to the bearing ele ments above enumerated.

Referring again to the film engaging drum 30, the surface of the drum is provided with two spaced bands 65 and 66 of friction material such as natural or synthetic rubber. These bands on drum 30 are in alignment with ribs 6'! and 68 provided on the surface of sound head 2|.

The film l3 passes between sound head 2| and the drum 38 as best shown in Figs. 6 and 8. The film at this point is being advanced at a more or less uniform velocity by driving sprocket 21 (Fig. 1), and the film, through the two-way frictional relationship with drum 30 provided by bands 65 and 65, causes corresponding rotation of shaft 32 and associated flywheel 33.

In order that proper pressure is exerted between drum 30, film l3 and sound head 2| to insure the desired two-way frictional drive relationship between film l3 and drum 3!], we provide a spring 10 (Figs. 2 and 6) extending between the pivoted flywheel enclosing portion 40 of housing 34 and the fixed side 36 of the projector. Means permitting adjustment of spring 18 is provided by associated bolt II that is threaded through projector side 36, the bolt H having a locking nut 12 as shown. Adjustment of bolt 1| controls the tension of spring 10 to vary the pressure exerted by drum 38 against film |3, thus to permit adjustment to insure proper operation of the stabilizer. Also, spring 10 permits selective separation of drum 30 from sound head 2| so that the film may be readily inserted or removed, th spring thereafter automatically restoring the stabilizer to condition for stabilizer operation.

Referring to Figs. 8 and 9, it will be seen that the bands 65 and 68 of friction material are somewhat deformed or flattened out upon contact with film |3. Thus areas of contact are provided to insure a substantially positive frictional drivin relationship between the film and drum 30. Therefore, the lineal velocity of film |3 is translated into corresponding angular velocity of drum 3E), shaft 32 and the associated flywheel inertia member 33.

During projector operation, the inertia member 33 develops an angular velocity corresponding generally to the average lineal velocity of film I3. Then as fluctuations occur in the projector that vary the speed of the film driving sprocket 21 to consequently affect the lineal velocity of film IS, the rotating inertia member tends to oppose and moderate the fluctuations, thus maintaining the velocity of film travel at a comparatively uniform rate. It will be understood that the inertia member is capable of either increasing or decreasing th film velocity depending upon the sense of the fluctuations in the mechanical film drivin ystem. The substantially constant film velocity thus provided is, of course, reflected in improved performance of the sound reproduction charac teristics of the projector.

. From the above description it is thought that the construction and advantages of this invention will be readily apparent to those ,skilled in the art, Various changes and modifications may be made without departing from the spirit or losing the advantages of the invention.

Having thus described the invention, what we claim as new and de ire to secure by Letters Patent is:

1. In a sound motion picture projector having a stationary sound head, a stabilizer including a flywheel and a film contacting drum connected thereto, said drum having a friction surface for engaging the film on said sound head in a twoway driving relationship, a supporting structure for said flywheel and drum having bearing means permitting free rotation of said flywheel and drum, pivotal means connecting said supporting structure to the body of the projector at a point remote from said drum, and means normally urging said drum into driving relationship with the film on said sound head.

2. A film velocity stabilizer for a sound motion picture projector including a sound head about a portion of which the film passes during scanning, a rotatable drum adapted to engage the film on said sound head in a two-way driving relationship, pivotal means connecting said drum with the projector, yieldable means urging said drum against the film, and an inertia member driven by said drum and operable to oppose and moderate fluctuations in film velocity.

3. In a sound motion picture projector having a stationary sound head: a stabilizer for insuring substantially constant velocity film travel at the point on the sound head where the sound track is scanned, said stabilizer including a shaft and an inertia member driven thereby, a supporting structure in which said shaft is rotatably mounted, a drum carried by said shaft, said drum having a friction surface for engagement with the moving film as the latter travels over said sound head, pivoted means connecting said supporting structure at a point remote from said drum to the body of the projector whereby the axis of said drum may be pivoted toward or away from said sound head, and yieldable pressure means normally urging said drum toward said sound head to maintain a two-way friction driving relation between said drum and the film during projector operation.

4. A film velocity stabilizer for a sound motion picture projector including a sound head about a portion of which the film passes during scanning, means remote from said sound head for driving said film at a more or less uniform velocity, a rotatable drum adapted to engage the film on said sound head in a frictional two-way driving relationship, pivotal means connecting said drum with said projector, yieldable pressure means urging said drum against the film and an inertiau member driven by said drum to oppose and moderate fluctuations in film velocity.

JACK BRISKIN. CONRAD PETO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,801,472 Whitson Apr. 21, 1931 1,998,931 Ke11ogg Apr. 23, 1935 2,026,625 Geyer Jan. 7, 1936 2,092,185 Ross et a1 Sept. 7, 1937 2,108,398 Allen Feb. 15, 1938 2,183,440 Barnicoat Dec. 12, 1939 2,204,887 Dewan June 18, 1940 2,258,759 Heacock Oct. 14, 1941 2,261,410 Perez Nov. 4, 1941 2,351,725 Wack June 20, 1944 FOREIGN PATENTS Number Country Date 420,223 Great Britain Nov. 28, 1934

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